大气压直流微等离子体辅助液相合成和液相修饰纳米粒子研究

Nanoparticles have a wide variety of potential application in biomedical, optical and electronic field due to their high surface area to volume ratio, size-dependent properties. The synthesis and surface engineering of nanoparticles are mainly carried on in liquid. Atmospheric-pressure non-equilibrium plasma is characterized with vacuum free, high electron temperature (several eV), and low gas temperature (room temperature), has potential application in plasma assisted liquid phase chemical reaction. In this proposal, atmospheric-pressure DC microplasma has been introduced to liquid phase engineering of silicon(si) and silicon carbide (sic) quantum dot as well as liquid phase synthesis of gold, silver nanoparticles and Au-DNA probe in liquid. Optical Emission Spectroscopy will be used to diagnose the plasmas, the model employing COMSOL multiphysics finite element modelling software as well as PIC-MC based on XPDP1 and XOOPIC will be developed to simulate the atmospheric-pressure dc microplasma, plasma density and electron temperature of microplasma will be studied as a function of the inner diameter of the hollow cathode, the gas flow, the discharge power and the gas composition (argon, helium, gas mixture of argon and helium). Optical absorption properties and photoluminescence properties of nanoparticles will be monitored by ultraviolet-visible (UV-vis) absorbance spectroscopy and photoluminescence measurement; Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy will be used to identify the chemical group attached to the nanoparticles surface, and by Transmission Electron microscopy (TEM), size and phase structure of nanoparticles will be imaged. Coupling non-equilibrium plasma chemistry with non-equilibrium wet chemistry, effect of electrons density and electron energy on atmospheric-pressure dc microplasma assisted liquid phase chemical reaction will be investigated. The research will be helpful to understand the mechanism involved in plasma-liquid interactions, and will lead the way to precision synthesis with accurate control over nanomaterials morphologies.

纳米粒子由于其表面效应、体积效应和量子尺寸效应，在生物医学、光电、能源、化工等领域具有重要应用。目前，纳米粒子合成和修饰主要在液相环境中进行。大气压非平衡低温等离子体具有无需真空、气体温度维持在室温、电子温度达到几个电子伏的特点，在辅助液相合成和液相修饰纳米粒子方面，具有潜在应用价值。本项目针对金、银纳米粒子、Au-DNA探针的合成和Si和SiC量子点的修饰,进行大气压直流微等离子体辅助液相化学反应研究。项目用发射光谱法诊断等离子体，用comsol软件和PIC-MC方法模拟等离子体，实验和理论研究放电参量对等离子体特性的影响；用紫外可见吸收光谱、光致荧光光谱检测反应溶液的光吸收、光致荧光特性；用FTIR、Raman光谱和TEM表征纳米粒子表面基团、纳米粒子尺度和结构；结合对等离子体非平衡特性和对液相非平衡化学反应动力学的分析研究，探索等离子密度和电子温度对液相合成和液相修饰纳米粒子的影响。

相比于应用于半导体产业低气压等离子体，常压微等离子体不需要真空泵设备因而能够方便地实现集成化和便携化。尽管如此，要获得密度、电子温度和电子、离子能量谱可控的等离子体仍是现代等离子体物理中的一大难点，其主要原因在于我们对等离子体动力学和非线性性质理解不够深入。课题主要研究常压微等离子体的热力学性质、不稳定性和非线性演化。主要研究成果包括研究了微等离子体氮气的振转温度随放电电流、气体流量和成分、不锈钢毛细管内径、放电间距等的变化；光成像、光谱方法获取二维空间解析的微等离子体中氮气的自发辐射，得到二维温度分布，辅以饱和图像，发现双层放电现象； 研究发现微等离子体与水电极的相互作用驱动了微等离子体的非线性演化。.常压微等离子体无需真空，可用于处理液体样品，辅助液相化学反应，推动电化学、等离子体科学、流体力学和生物医用技术的发展。课题研究常压微等离子体辅助电化学反应制备金、银纳米颗粒，研究金、银纳米粒子的合成机理，以及对金、银纳米颗粒尺寸和尺寸分布的控制，其中论文Nanotechnol. 2013, 24: 095604被该期社评 [Nanotechnol. 2013, 24: 090201]大篇幅正面报道。基于常压微等离子体辅助电化反应技术，首次在无化学还原剂的条件下，实现了单步、绿色方法合成金银合金纳米颗粒，同时辅以在线紫外可见吸收光谱，考察了金银合金纳米颗粒的合成过程，该研究成果作为内封面论文发表在ChemComm 2014, 50(24): 3111上。此外，以果糖水溶液为反应溶液，首次提出一种简便、快捷的制备碳量子点的方法，所获得碳量子点尺寸为3.5 nm，在紫光照射下，呈绿色荧光（Green Chem. 2014, 16: 2566）。与此同时，实现基于等离子体辅助电化学反应技术的荧光碳点合成，该研究成果作为封底论文发表在Plasma Process. Polym. 2015, 12: 59上。.上述研究成果为深入研究常压微等离子体物理、常压微等离子体和液体相互作用、以及常压微等离子体在纳米材料制备中的应用，提供了理论和实验基础。